Speed issue

[#1]

I know, there's different stickies about speed issues, but it all looks rather technical, and I'm a middle aged woman with limited knowledge in these things.
What I do know is that my broadband speed is fluctuating. A lot of the time over the past couple of evenings it's around, or less than 200Kbps, at best, and what it normally is, is over 2000Kbps.
It's a heck of a fluctuation, and very frustrating.
Before I start thinking about getting a new router, I was wondering if there's any way to check if there's anything at your end that is causing this.
It reminds me of when i had my old product with you, and at the end of the month, when i'd used up my limit, i'd have a few days of slow evenings. But that's why I changed, and thought I had it covered now. Is there something I'm missing?
Thank you for your time.

[#2]

Hi there,
The line profile is still fine, and there's no drops in connection that I can see. Likewise you're nowhere near your usage limit so that's not a worry either.
I suspect last night you were seeing the effect of the Apple iOS5 update hitting our network (there's a blog with details on just how much traffic there was here.
If there's been any other slowdowns though please let us know as there might be a line fault, in which case BT speed test results would help a great deal.
Hope that helps,

[#3]

Thank you, I was wondering if the Apple update might be affecting things, but wasn't sure. Luckily my own upgrade on that worked fine once I waited for a time when most of America would be in bed
I'll wait a few days till it settles down, and see if there's still an issue.
Thanks again